Carbon dioxide emissions of green roofing case study in southern Brazil

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1 Carbon dioxide s of green roofing case study in southern Brazil Giane de Campos Grigoletti, DrEng Marcos Fabrício Benedetti Pereira, MEng [Universidade Federal de Santa Maria] grigoletti@smail.ufsm.br [Universidade Luterana do Brasil] ABSTRACT Nowadays there are several efforts in define bon dioxide s of buildings components and materials. This data shall be in accordance with local building technology or methods of construction. Therefore studies of local alternatives are important. This work presents results of bon dioxide s for two solutions of usual green roofing in southern Brazil. The method considers production of main inputs, transport from point of sale to the site of construction, workmanship transport. The two green roofs are compared with ceramic and asbestoscement tiles solution. The data were obtained by surveys, interviews with owners and scientific literature. The building materials, distances of transport were quantified. The results demonstrate that the bon dioxide s are larger than the s of the conventional roofing and the main contribution is due to the transport of components and materials from the point of sale to the site of construction. However, we must consider that the green roofing has a high potential for the bon sequestration, promotes thermal resistance, humidify and filter the air, reduce the urban surface temperatures. INTRODUCTION Civil construction is responsible for 4% of energy demand and 38% of air s that contribute for global warming. However there is 3% to 5% of potential for reduction of energy consumption and 35% for reduction of air s [1]. In Brazil the civil construction has substantial participation on greenhouse gases. Excluding the bon dioxide (CO) emitted by burnoffs, the building construction represents a quarter of significant air s, either by chemical reactions of industrial processes of materials or by the energy sources involved in these industrial processes []. Further, the materials transportation, mainly by s with fossil fuel, contributes significantly for CO s [3]. Table 1 illustrates the CO s coefficient (Kg CO eq) for the mainly fuels used in Brazil []. Table 1. CO s due to some fuel sources fuel source emissões de CO (kg CO/GJ) diesel oil 79,8 natural gas 5,6 petroleum coke 7,6 other sources derived of petroleum, electrical energy 18,1 fuel wood 81,6 Table ilustrates the energy in some construction materials expressed in percentage according to []. The use of energy in industrial processes also significantly contributes for CO Author A is a professor in the Department of Architecture and Urbanism, Santa Maria University, Santa Maria, Brazil. Author B is a professor in Brazilian Luterane University, Santa Maria, Brazil December 14, CEPT University, Ahmedabad 1

2 s; therefore the consideration of production s is important in the life cycle of construction materials. Table. Percentage of energy due to source for some materials construction material/source diesel oil natural gas coke other sources electrical energy wood sand 99 1 mortar 86 4 ceramic 4 85 cement asbestos waterproofing substances polymer The choice of the best environmentaly sound building technologies promotes the envinronmental impacts reduction, such as energy consumption and toxical gases s [4]. Technologies must be in accordance with local and regional traditional technology and disponibility of natural resources and industrialized local materials. Therefore the study of local solutions is important to achieve the building environmental performance. In this study green roofs are understood as vegetal intentionally incorporate on top of buildings. They have been pointed as alternatives more sustainable if compared with conventional roofs, such as tile and asbestoscement roofs. There are many vantages associated to green roofing, such as natural top ground, life cycle extended, better thermal performance and consequently building occupants comfort more acceptable, reduction of urban heatisland effect, bon sequestration, among others [5]; [6]. A negative factor associated to green roofs regards to the water comsuption. This aspect is not studied in this research, but some authors pointed that there are benefits to manage stormwater in order to restore the capacity of water retation lost by excessive paving of in cities [7]. It is possible to reduce about 6% of runoff for rain water captation. Further, the use os plant species that require little irrigation can be reduce the water comsuption, one of negative factors associated to green roofing [7]. In Brazil some studies about green roofing has been already enhanced. Through computational simulation [8] and prototypes submitted to measurement [9] the potential of green roofs for water catchment and retention was verified. Also was verified the viability of green roofs for lowcost housing [1]. A research concerning to occupants satisfaction indicated that the need for constant maintenance was one of the problems more mentioned [11]. However there are a few studies about the environmental impacts of green roofs mainly referring to CO s. This study aims to contribute to this issue through the quantification of bon dioxide s of four roofs commonly built in Brazil, two green roofs built in two different regions, provincial medium town and industrial city, and two conventional ceramic and asbestoscement roofing in order to compare their environmental performance due to bon dioxide s. Additionaly the bon sequestration potential was quantified in order to verify this important contribution of green roofs for sound environments. METHOD Selected green roofs The green roofs are approximately km away each other (with different proximities of industries that produce the building materials involved), they are selected in accordance with the occupants permission to access the necessary data for the life cycle inventory, the construction system involves little labour and artisanal method. The ceramic tiles and asbestoscement roof do not have the same thermal insulation, since the owners have chosen the green roofs for aesthetic and environmental sustainability, without refering their thermal performance. The Figure 1 ilustrates the green roofs studied December 14, CEPT University, Ahmedabad

3 grass organic sand crushed asphalt fabric rock concrete slab Figure 1 grass organic water proofing pebble water proofing crushing concrete slab (a) Layers of green roof located in a big city, (b) in a mendium town in country. Inventory The data for the inventory were obtained from interviews with the owners of analysed houses, invoices, private diaries and reports elaborated by owners, regular direct observations, measurements during building production process. Layers constituting the roofs, quantitative of materials, products points of sale, places of production of listed materials, distances of production, sale and jobsite area, materials modal transportation were collected. The demand of labour and the distances between jobsite, workers housing, means of transport also were measured from interviews and data registered by owners. The distances were obtained from virtual maps. Quantification of bon dioxide s Contribution of different energy inputs was defined for constituting s and materials. For each material, the energy CE was computed, the percentage of each significant source present in material production was also computed, obtained from [], and is represented by P%. The individual contribution of each source was obtained by the product of energy and the individual bon dioxide source contribution named coefcosource obtained from []. The somatory of individual contributions is the bon dioxide s ECO represented by Equation 1. ECO = [CE (MJ) P%/1 coefcosource] (1) where ECO is the bon dioxide, kg CO; CE is the contribution of different energy inputs, MJ; P% is the percentage of a kind energy in production process, %; coefcosource is an index representative of CO of energy source, kg CO/MJ. Since it was not possible to determine the characteristics of vehicle used as mean of transport and the kind of fuel, the indices established by [3], which studied bon dioxide s for Brazilian transport, were considered as reference. The mentioned author considers that it is possible to determine the CO s with an admissible error considering the distances and a medium factor according to type of transport. The bon dioxide index for transportation from place of production to place of sale, with heavy transport, was considered equal to.895 kg CO / km [3] since that is the conventional transport for construction materials in Brazil; for transportation from place of sale to jobplace (conventionaly transport of light load in Brazil) was considered equal to.16 kg CO / km [3] by the same previus reason. The bon dioxide related to mean transport for each material was calculated using the Equation. material transport = CO/km x distanceprod sale + CO/km x distancesale jobplace () 1618 December 14, CEPT University, Ahmedabad 3

4 The Equation 3 was used for calculating the s due to transport of workers. The dioxide bon index per day for mean transport was considered equal to.16 kg CO / km.day, energy was considered equal to 15 MJ / kg and the weight for worker is equal to 7kg. WTCO = EE x weight x distancehome workjob x worked days x CO/km where WTCO is the worker transport, kg CO; EE is the energy, MJ/kg; distancehome workjob is the distance between the home and the workplace, km; weight is the transported weight, kg; CO/km is the bon dioxide s per kilometer due to worker transport, CO/km. Carbon sequestration Addionally the potential for bon sequestration was calculated in order to verify one of main environmental contribution of green roofing. The larger bon sequestration for grass with cm of substrate for plant growth is considered equal to.945 kgco / (m.year) [1]. The mentioned value was multiplied for the area of each green roof. Total calculated bon dioxide for each green roof was divided for the index in order to obtain the number of years necessary to sequester. RESULTS Table 3 presents the bon dioxide s due to materials production and Table 4 s due to transport for the green roof located at the big city (green roof 1) with 8,41m of surface. Table 3. Carbon dioxide s due to material production for green roof 1. relative area or density mass CO s volume (kg/m³) (kg) energy energy (MJ) (kgco) (MJ/kg) asphalt fabric 8.41m , mm crushed.8m rock sand.57m organic.75m m garden grass m 1.5 1,53.7 (6%) garden grass 11.48m 1.5 1,33. (4%) 4, , per 33.6MJ/m 1.3kgCO /m m 1618 December 14, CEPT University, Ahmedabad 4

5 Table 4. Carbon dioxide s due to material transport for green roof 1. emissio CO transport distance n CO transport distanceprod sal COprod sal prod sal sale jobplac sale jobpla e (km) sale jobplace e (km) ce (CO e (CO kg) e (KgCO) kg) asphalt fabric 4mm crushe d rock , , ,434. 1, ,89.66 sand organic garden grass 1 (6%) garden grass (4%) per m wheelbarro w wheelbarro w 45.39kgCO/m The major s are due to asphalt fabric that is the component with industrial process more complex among the green roof s; involves large energy inputs; with centralized production. Therefore replacement of that is a possibility in reducing de CO impact. Table 5 presents the bon dioxide s due to worker transport for the green roof 1. Table 5. Carbon dioxide s due to workers transport for green roof 1. weight of CO distancehome workjob worked days transport owner worker transported workers (kg) 14 Kg 14 Kg (km) energy (MJ) (kg CO) For the ceramic tile roof built in the big city, the main contributions are due to production of ceramic tiles ( kgco) and due to transport of truss materials (peroba wood) (1,1. kgco). In this case, the use of wood which production is strongly centralized (with environmental license) contributes significantly to bon dioxide s. For the asbestoscement roof built in the same place, the main contributions are due to transport of truss materials (1,1, kgco), since there are local industries that produce fibercement tiles. Table 6 presents the bon dioxide s due to materials production and Table 7 s due to transport for the green roof located at the medium town (green roof ). Table 6. Carbon dioxide s due to material production for green roof. relative CO area or density mass (kg) volume (kg/m³) energy energy (MJ) (kgco) (MJ/kg) waterproofing 45.8 litres 1.3 (kg/l) , pebble crushing waterproofing coating.3 m³ 1,3, 56.6 m² m³ 1,4 4,76 garden grass 56.6 m² 1,5 5, per m 1618 December 14, CEPT University, Ahmedabad 4, MJ/m 4.kgCO/m 5

6 Table 7. Carbon dioxide s due to material transport for green roof. transport transport distance CO distance CO CO sale prod sale (km) sale prod sale prod sale sale jobplace jobplace (CO kg) (km) (CO kg) (CO Kg) jobplace waterproof. pebble crushing waterproof. coating 165 1, , ,431 1, ,81.48 garden grass,,696, , kgco/m per m Table 8 presents the bon dioxide s due to worker transport for the green roof. Table 8. Carbon dioxide s due to workers transport for green roof. weight of CO distancehome workjob worked days transport owner worker transported workers (kg) 8 Kg 8 Kg (km) energy (MJ) (kg CO) In the same way of the precedent green roof 1, the major s are due to more industrialised component that is the waterproofing s. The use of two waterproofing s is critical for the poor performance of this roof. For the ceramic tile roof built in the medium town, such as for the big city, the main contributions are due to production of ceramic tiles (958.1 kgco) and due to transport of truss materials (peroba wood) (1,178. kgco). In this case, the use of wood which production is strongly centralized (with environmental license) contributes significantly to bon dioxide s. For the asbestoscement roof built in the medium town, the main contributions are due to transport of truss materials (1,178. kgco). The incorporated cement in the asbestos tiles is responsible for kgco s. The Figure 3 illustrates the s per square metres due to the six roofs, green, asbestoscement, ceramic. In relation to transport materials both green roofs present lower performance than ceramic and cementasbestos conventional roofs. This result is due to presence of s based on fossil source (asphalt fabric and water proofing ) with centralized production. In relation to bon dioxide s produced from manufacturing the green roof 1 is more unsustainable due to asphalt fabric, presenting best performance only compared with the ceramic tile roof. Production of ceramic tiles envolves large energy for burning and transport due to their weight since this type of roofing has large energy and bon dioxide s. The cementasbestos tile results in the best performance for the case study in the big town because there are local industries for this material. The three roofs type located in the town far of production regions present the lower contribution in CO s what is an unexpected result since is further away from production centers. This result demonstrates the importance of contextualized solutions. Green roof is technically simpler; a despite of using a water proofing with large energy and bon dioxide s, it requires less amount of material to fullfil the same function comparatively with roof 1. The s associated to worker transport are insignificant compared to production and transport materials due to artisanal and autoconstruction process, reforcing the use local workforce and techniques December 14, CEPT University, Ahmedabad 6

7 6, 5, 4, 3,, 1,, transport materials production transport workers CO (kgco) Figure 3 Partial and CO s due to different analised roofs per square metres. Considering the three contributions analyzed, transport materials, production, and transport workers, there is little difference between the three roofing in the medium town, which is does not do in the case of roofing in the big city where the cementasbestos is the best solution. It takes the green roof 1 about 61 years for bon sequestration due to production and transport of materials and workers. For the green roof, it takes about 5 years. These results demonstrate that the main benefit of green roof is obtained in very long timelag, which counters to principal benefit associated to green roofs. CONCLUSION Through results the green roofs present large CO s due to use of s based on polymers or fossil source materials which production involves large energy and several s that contributes for greenhouse. It pointed to need to replace the waterproofing based on fossil source for another one more environmentally sound. For the case studies illustred material transport is responsible for the largest s for six simulated roofing. Results reinforce the importance of choosing local and regional technologies, materials, and workforce. The cementasbestos roof has the best performance relative to bon dioxide s; it flies in the face of common sense in considering the green roof necessarily an environmently good solution. Furthermore, one of benefits associated to green roofs, the bon sequestration, is reached in a long time opposing to general idea of sustainability. Green roofing has been considered as a building system with low environmental impacts. The analyses of bon dioxide s demonstrated that it has lower performance than the conventional solutions even if were regarded the potential for bon sequestration. However the easiest solution adopted for the conventional roofing, without a thermal insulation, collaborate for the results achieved. REFERENCES [1] HOBALLAH, Arab. 1. Building design and construction: forging Resource Efficiency and Sustainable Development. UNEP. [] TAVARES, Sérgio Fernando. 6. Metodologia de análise do ciclo de vida energético de edificações residenciais brasileiras. Doctoral Thesis. Santa Catarina Federal University (UFSC) December 14, CEPT University, Ahmedabad 7

8 [3] BARTHLOMEU, Daniela Bacchi. 6. Metodologia de análise do ciclo de vida energético de edificações residenciais brasileiras. Doctoral Thesis. São Paulo University (USP). [4] BRIBIÁN, Ignacio Zabalza; CAPILLA, Antonio Vallero; USÓN, Alfonso Aranda. 11. Life cycle assessment of building materials: Comparative analysis of energy and environmental impacts and valuation of the ecoefficiency improvement potential. Building and Environment, 46: [5] HOPKINS, Graeme; GOODWIN, Christine. 11. Living Architecture: Green Roofs and Walls. Collingwood. CSIRO. [6] SNODGRASS, Edmund C.; MCINTYRE, Linda. 1. The Green Roof Manual: A Professional Guide to Design, Installation, and Maintenance. London. Timber. [7] TASSI, Rutnéia; et al. 14. Green roof: a sustainable alternative for stormwater management. Ambiente Construído, Porto Alegre, 14, n. 1: [8] SANTOS, Pedro T. da Silva; et al. 13. Green roof: performance of the constructive system in the reduction of runoff. Ambiente Construído, Porto Alegre, 13, n. 1 : [9] BALDESSAR, Silvia Maria Nogueira. 1. Telhado verde e sua contribuição na redução da vazão da água pluvial escoada. Master Thesis. Parana Federal University (UFPR). [1] OLIVEIRA, Eric Watson Netto de. 9. Telhados verdes para habitações de interesse social: retenção das águas pluviais e conforto térmico. Master Thesis. Rio de Janeiro Estadual University. [11] KIST, Rubens Sallaberry. 11. Coberturas verdes sobre edificações: avaliação da satisfação de moradores de um condomínio horizontal na cidade de Porto Alegre. Monography. Rio Grande do Sul Federal Univesity (UFRGS). [1] SEGNINI, Aline; et. al. 7. Sequestro de bono em solos com gramíneas. Revista Circular Técnica. São Carlos. EMBRAPA. 41. set December 14, CEPT University, Ahmedabad 8